eddie_993

Just changed the master cylinder and kinematic lever in my car and now the pedal won't return at all. I am guessing and hoping this is due to air bubbles.

I have been reading up on different ways to bleed the system and it seems like the best way to do it is to reverse bleed the system due to the natural tendency of air bubbles to travel upwards. Few questions:

1) Anyone done this before on a 993? As far as I saw, you can use either a Motive Power Bleeder or a simple oil can.

2) I don't know what the interior design of the master clutch cylinder looks like so is it recommended that the pedal be depressed or not? I believe it was on a 996 forum that somebody was recommending to have the clutch pedal depressed due to the internal design.

Thanks for your help!

Mike J

I pressure bleed the clutch circuit, but be very careful, the level of the reservoir does not have to drop very far before you start to suck air - that might be your problem.

The clutch pedal does not have to be depressed, and if it is, it will not allow fluid to flow from the reservoir.

I use a pressure regulator and a custom cap for the brake fluid/clutch fluid reservoir - set the pressure to 5-10 psi, and bleed away at the slave cylinder. Keep the reservoir as close to full as possible.

Nothing special

Cheers,

Mike

kjr914

Eddie,
Been there, done that.... So I know the pain.

Just get a friend to work that clutch pedal while you work the bleeder nipple and catch can on the slave cylinder. Only go 1/2 way down with the pedal, using both hands on the pedal to prevent snapping to the floor. Have the person working the pedal frequently check the fluid in the BACK section of the reservoir to prevent getting air in (which is exactly what you have now).

The key is the back (rear of the car) section (approx 0.74") of the brake fluid reservoir)is seperated out for the clutch slave. VERY HARD to see. But you need to monitor it closely, and fill frequently.

Mike J

You an also do a full stroke if using the pedal - just attach a small rope to the pedal and the pumper can pull the pedal back pretty easily... :-)

IXLR8

Not on a 993, but I have seen it done on Cessnas where I was instructing and wrenching at my local flying club. The AME used an oil can.

I myself use a Motive Products Power Bleeder. Well worth it. Pelican Parts had the lowest price when I bought mine and free shipping by the time I added a few more dollars to my order.

eddie_993

It seems like everyone is pointing in the same direction more or less. I had just read that the reverse bleeding technique is much more efficient.

I will have to order one of those Motive Power Bleeders from Pelican Parts. I'm really surprised no local auto parts stores have them or anything similar. I ended up buying a vacuum bleeder from Pep Boys but seems like that is fairly useless so will be returning that.

This is getting frustrating, over 5 weeks of not having driven the car

Thanks for your input guys!

bruce7

Hi Eddie,

I don't think it's necessary to do reverse fluid injection (RFI) to bleed the clutch circuit on a 993.
Using pressure flushing should remove all the air in the circuit.

I use a tool called a Phoenix Injector which is shown in one of the photos below.
I've made custom caps for the brake fluid reservoir and the Porsche brake fluid can.
I also use a special waste collection bottle with a black flow prevention valve.

I've found that after pressurizing the reservoir you have go under the car and
hold the bleed nipple after opening to get a good flow into the waste container.

Also, here is a picture of a clutch master cylinder taken apart to show you how it is made.

On the 986 and 987 you do depress the clutch during bleeding using a pedal depressor and then pump it by hand after you close the bleed nipple.
However, on the 993 you do not depress the clutch during bleeding.

I've developed and used the same system to flush the hydraulic system on 986, 987 and 993 cars.
The only difference is the clutch pedal position during bleeding.

-bruce

eddie_993

Hey Bruce,

Thanks for the pics, very helpful. I saw that Phoenix V12 system on Youtube, they actually give a good explanation of the different bleeding methods (normal, reverse and vacuum). Please correct me if I'm wrong, but essentially you have the same system as a Motive Power Bleeder except it's a handheld piston.

I was going to have the clutch slave cylinder changed out by a mechanic, however, it seems like the car has different plans for me

kjr914

Instead, for the $60, you can just buy (alot of) beer for the friend working the pedal!

For the clutch, you will probably have to refill the fluid resovoir so you'll have to depressurize the Motive at some point (there are mods to keep the pressure in the Motive bottle somewhere here on RL (from Alex or Andreas or one of the other handy folks)). So, this is why I suggest using a friend. And you don't have to drink alone while you are in the garage!

Motive is good for when you have to do bleeding alone in the garage, however.

bruce7

Eddie,

Similar maybe, but definitely different. When the Motive is used in the wet mode,
you are using air pressure to push the fluid out and into the hydraulic
system. When used in the dry mode, you are again using air pressure to push
fluid already in the reservoir. It really is nothing more than a fancy bug sprayer.

With the Phoenix Injector, you are using mechanical force to push directly
against the fluid, injecting it into the hydraulic system.

It is also easier to clean afterward by flushing with denatured alcohol vs.
swabbing out a bottle that was used in the wet mode.

It also enables a single person to do the flushing and bleeding without requiring
a helper.

In a professional system that does use air pressure, they will separate the fluid
from the air with a rubber bladder to prevent possible aeration. Ate makes one
and so others. But it is more suited to a shop doing frequent brake jobs.

Hope that helps,

-bruce

eddie_993

Keith: Soonest I'll be able to get a friend to help out will be in a week and a half but I might just wait since I need his help anyways. Just seems like there's a lot of pumping to do but that's what the beer is for

Bruce: Thanks again for your help. Those Phoenix things are a bit too pricey but I guess worth it if you do not want to pump away or use a friend. I'm sure they work great, though.

Mike J

I would advise against the manual pump technique, especially for someone not experienced - its way to easy to pump a longer stroke and get the master cylinder seals into corroded areas, causing all kinds of damaged.

If you pressurize the system and use pressure to move the fluid, no pumping or wear of the seals happens.

Cheers,

Mike

gtroth

Yeah, mine did that too
Get the motive and bleed a lot. Push and release the pedal a few times during the process and bang on the pedal with your fist to get any sticky bubbles moving.
I use the motive wet (filled) so the reservoir won't run dry. And it is handy to open and close the valve by hand once it's cracked loose. I also like to hold it open with my hand during the process, but I am sitting on a stool with the car on a lift.
Good luck- you'll have a much better time with the motive.

ReinerFink

I am always suprised how terrible the fluid coming out of the clutch slave looks. Are the seals that much worse than brake calipers?

eddie_993

Talking out of my a** here but maybe it's because the clutch pedal is pressed more often?

City driving I would say on average I hit the clutch pedal 4 times for every time I hit the brake pedal.